In gas turbine engines, air is compressed at an initial stage, is subsequently heated in combustion chambers, and the hot gas so produced passes to a turbine that, driven by the hot gas, does work which may include rotating the air compressor.
In a typical industrial gas turbine engine, a number of combustion chambers combust fuel. Hot gas flowing from these combustion chambers is passed from a combustor basket and into respective transitions (also referred to as ducts or transition pieces) through an interface between the combustor basket and the respective transition. As the hot gas flows from the combustor basket, through the interface and into the respective transition, a number of design factors of the interface may affect performance criteria of the gas turbine engine. For example, compressed air external to the interface has a tendency to pass through a gap formed by the interface, and thus the interface is designed with some degree of sealing. Additionally, a parameter of the flow of hot gas through the interface, such as a flow direction through the interface, may have an impact on performance criteria of the gas turbine engine. Consequently, the design of such an interface has an impact on various performance criteria of the gas turbine engine.
Conventional gas turbine engines have been designed with an interface between the combustor basket and the transition. FIG. 1 provides a cross-sectional view of a prior art interface 110 where the combustor basket 112 is positioned within the transition 114 of a gas turbine engine 116. A flow 115 of hot gas which passes from the combustor basket 112 and into the transition 114 experiences a change in diameter 123 as the flow 115 passes from a smaller diameter 125 of the combustor basket 112 into a larger diameter 127 of the transition 114. Note that the change in diameter 123 depicted in FIG. 1 is half of the total change in diameter experienced by the flow 115 of hot gas passing from the combustor basket 112 to the transition 114. A spring clip seal 120 is positioned within a gap 121 between the combustor basket 112 and the transition 114, to prevent a flow of compressed air from a region 117 outside the transition 114 from mixing with the flow 115 of hot gas within the transition 114.
Although conventional gas turbine engines do provide an interface between the combustor basket and the transition, the conventional interface design has notable drawbacks. For example, the selection of sealing arrangements for the interface is primarily limited to the spring clip seal 120, based on the positional arrangement of the combustor basket 112 within the transition 114. Accordingly, there is little or no latitude to select from a variety of sealing arrangements at the interface 110, in order to achieve a desired level of sealing. Additionally, for example, as the hot gas flow 115 experiences the change in diameter 123 in passing from the combustor basket 112 into the transition 114, a recirculating hot zone 119 is produced, where the dwell time, or duration over which the fuel/air mixture within the flow 115 burns, is extended, which may in-turn increase a peak temperature of the flow 115 above a maximum threshold, resulting in high stresses. Additionally, the limited selection of the spring clip seal 120 does not provide uniform sealing around the circumference of the interface between the combustor basket 112 and the transition 114, and thus the combustor basket 112 and the transition 114 are not continuously aligned, resulting in uneven leakage around the circumference of the interface and an uneven change in the diameter 123 around the circumference of the interface resulting in combustion instabilities and/or high emissions.
Thus, it would be advantageous to provide an interface between the combustor basket and the transition, which avoids the shortcomings of the conventional interface design.